Cantaloupes rot in the afternoon heat on a field on the Jensen Farms near Holly, Colo., last month. Whole fruit contaminated with listeria have been blamed for 25 deaths in the worst food poisoning outbreak in the U.S. in a quarter century.

Now that federal investigators have identified dirty equipment, faulty sanitation and bad storage practices at a Colorado farm as the likely cause of a cantaloupe listeria outbreak that has killed 25 people, top U.S. food safety experts say there's one actor in this deadly drama that shouldn't be blamed: The consumer.

No amount of washing, scrubbing, bleaching or peeling would have cleaned cantaloupes contaminated by Jensen Farms' packing practices enough to remove listeria bacteria that has sickened at least 123 people and killed 25 in the deadliest outbreak in a quarter-century.

"There's nothing consumers could have done," said Dr. Doug Powell, a professor of food safety at Kansas State University in Manhattan, Kan.

Federal Food and Drug Administration officials reported Wednesday that standing pools of water, inaccessible drains, hard-to-clean equipment and failure to cool cantaloupes fresh from the field before placing them in cold storage all likely contributed to the growth and spread of four strains of listeria bacteria at the Jensen Farms packing site in Granada, Colo.

The cold, moist environment maintained over time is exactly what listeria needs to thrive, said Dr. Mike Osterholm, director of the Center for Infectious Disease Research and Policy and a food safety expert at the University of Minnesota.

In addition, listeria could have been introduced into the packing center from sporadic bacteria in the field or from a dump truck that hauled culled cantaloupe back and forth to a cattle yard and then parked next to where the whole melons were being processed. Cattle are known reservoirs for listeria.

The bacteria clearly contaminated a huge proportion of the more than 310,000 cases of cantaloupe -- between 1.5 million and 4.5 million fruit -- that were recalled by Jensen Farms in mid-September, said Powell.

"Given that 25 people are dead, this was a massive contamination to have that impact," he said.

It's not clear whether people were infected by bacteria that clung to the fruit's porous, bumpy rind, whether the germs somehow migrated into the flesh of the fruit, or whether people spread contamination through the fruit by slicing it with a knife, Powell said. Good hygiene and food safety practices can lessen the chance of infection, but the contamination shouldn't be there in the first place.

"The idea that this is the consumer's responsibility is just nonsense," he said. "What's missing is any verification that individual farmers are doing what they're supposed to be doing."

Preventing the conditions that allowed the outbreak to occur and continue is the primary goal of the FDA's ongoing food safety efforts said the agency's commissioner, Dr. Margaret Hamburg.

“If we’re to have a food safety system that truly prevents foodborne illness, we must all practice prevention,” she told reporters.

That's particularly incumbent on melon growers, who have felt the brunt of consumer fear as sales of cantaloupes have plummeted.

"Don't rely on paperwork if your brand relies on selling safe food," Powell said. "Any commodity is only as good as its worst grower."